1. Field of the Invention
This invention relates to dash mats. In one of its aspects, the invention relates to a dash mat with integral retainers for fastening a secondary layer thereto. In another of its aspects, the invention relates to a sound absorbing vehicle dash mat having integral retainers for fastening a sound absorber layer to a sound barrier layer to form the dash mat. In another of its aspects, the invention relates to a method for making a dash mat.
2. Description of the Related Art
In most contemporary automobiles, a steel firewall separates the engine compartment from the passenger compartment. To reduce the transmission of sound from the engine compartment through the firewall and into the passenger compartment, a dash mat overlies the firewall and retards the transfer of mechanical and sonic vibrations from the engine compartment into the passenger compartment through the firewall. The dash mat typically comprises a sound absorber layer, abutting the firewall, and a sound barrier layer abutting the sound absorber layer.
The sound absorber layer is commonly made from an open-cell foam to attenuate the mechanical vibrations. The sound barrier layer is commonly made from a relatively dense material, such as an elastomer, to block the transfer of sonic vibrations.
An outer surface of the sound barrier layer is typically in contact with a bottom surface of the vehicle carpet and extends beyond the carpet to an upper portion of the firewall behind the instrument panel.
It is common to attach the absorber layer to the sound barrier layer through the application of hot melt glue or spray adhesive. Adhesives that are capable of bonding the foam material to the elastomer are typically ozone depleting and must be handled with extreme care. Many of these types of adhesives are no longer being manufactured due to environmental concerns and new industrial standards. A technique known as heat staking has been used as an alternative to ozone-depleting adhesives. However, the layers must be properly aligned and temporarily fastened together before heat staking. It would be advantageous to attach the absorber layer to the sound insulating layer without the difficulties encountered with adhesives or temporary fasteners.